Preventive externment can rely on past convictions where the statute indicates retrospective reach and bona fide use.

Section 57 of the Bombay Police Act, 1951 was held applicable to convictions recorded before the Act came into force, because the provision authorised preventive action and did not create a new offence or impose punishment for past conduct. The words "has been convicted" were interpreted to include past convictions, subject to the statute's language and scheme. An externment order under the section must still be made bona fide and should rely on a conviction sufficiently proximate in time, depending on the facts. The High Court's contrary view on retrospectivity was rejected, and the matter was remitted for consideration of the remaining issues.

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Issues: Whether section 57 of the Bombay Police Act, 1951 could be applied to a conviction recorded before the Act came into force, and whether the externment order based on such past conviction was invalid on that ground.

Analysis: The section did not create a new offence or impose punishment for past conduct. It authorised preventive action to protect the public from persons previously convicted of specified offences. A statute of this nature may operate on past convictions if the language and scheme show such an intention. The use of the words "has been convicted" in section 57 was held to describe past convictions and not to confine the provision to convictions after commencement of the Act. The Court further held that an externment order under the section must nevertheless be made bona fide and must take into account a conviction sufficiently proximate in time, depending on the facts of each case.

Conclusion: Section 57 of the Bombay Police Act, 1951 was held applicable to past convictions, and the High Court's contrary view on retrospectivity was rejected. The appeal succeeded and the matter was sent back for decision on the remaining points.

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